Chromatography Lab Using illumina to extract fluorene and 9-fluorenone. 1. If th

Question

Chromatography Lab

Using illumina to extract fluorene and 9-fluorenone.

1.

If the polarity of the eluant is to be increased during column chromatography, the increase is normally made gradually. However, in this procedure, pure dichloromethane rather than intermediate mixtures of petroleum ether and dichloromethane was added to the column. Why is this variation from the usual technique acceptable in this case?

2.

The observed melting point of the 1:1 mixture of fluorene and 9-fluorenone should be relatively sharp, although lower than the melting point of either of the pure compounds. On the other hand, a 3:1 mixture has a broad meltingpoint range of about 60–90 °C. Explain these observations.

Explanation / Answer

One can move quickly to the polar solvents if you know your product is considerably polar. It doesn't affect the purity when the polarity difference between the reactant and products are large. In this case also large polarity difference is expected.

2. It's because the mixture become eutectic when you are having 3:1 mixture, hence it shows a broad range melting point.

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